Just read the procedure described above. It describes how alternative medicine practitioner Ernie Hubbard, who set the kale=bad meme rolling earlier this month, tested his suspicion that patients were poisoning themselves with kale. Ah yes, the trusty upside-down-notecard-on-a-desk technique! Where would science be without it?

As Julia Belluz explains, in her deft dismantling of Hubbard’s claims at Vox:

This approach has obvious flaws. The fact that people who have various symptoms also happen to eat kale is in no way proof that the two are linked. What’s more, the idea that kale might be the cause of everything from arrhythmias to gluten sensitivity seems suspect on its face. In fact, suggesting that a single item — one type of food — can explain a vast array of health problems is one of the hallmarks of a crackpot health theory. As William Toscano, an environmental health researcher at the University of Minnesota, told me: “Causality would be difficult to show because the diseases are complex and probably have multiple causes including genetic and epigenetic involvement.”

Hubbard also contacted us regarding a 2006 paper by Czech researchers that states “Some brassicaceous plants [a family of flowering plants that includes kale, broccoli, cabbage, among many others] commonly grown as vegetables behave as hyperaccumulators” of thallium. A co-author of that study confirmed to Vox that kale is a good accumulator of thallium, but that it is highly unlikely the plants would absorb enough to poison humans. We therefore have revised the statement that there are no studies supporting the theory that kale can serve a vehicle for thallium.